In certain forums on the web we find lists purporting to rank the
most dangerous and/or venomous snakes in the world. Unfortunately
one can take one's pick as there are a number - and none of them agree
with each other.

How accurate are they? How long is a piece of string?

The criteria for judging the most dangerous snakes
should be simple. In fact only one factor can legitimately be used -
human deaths attributed to the specific species.

Contributing factors would be the distribution of the species,
aggression, venom yield, toxicity of venom, habits of the snakes.

Obviously a fairly venomous species that is found in vast reaches
of the earth will kill more humans than a violently venomous species
known to live on only one inaccesible grassy knoll on an uninhabited
Patagonian island.

However when all is said and done - the only accountable factor MUST
be the body count of the species.

As to the most venomous we run into similar problems of definition.
The effect of snake venom is measured in mouse units. The standard test is
to measure how many standard sized mice a given weight/volume of venom will
kill. From there an estimation and extrapolation is made to a standard
70 kg human male.

The problems inherent here are:

venoms differ in their specific effects

venoms are often far more lethal to specific prey animals

venoms vary by area distribution, age, sex, time and season in
their toxicity.

the yield varies from specimen to specimen.

Fierce Snake

Australia's crop of highly venomous elapids feature high on many lists.
Yet Australia has had, over the last 20 years, a confirmed mortality rate
averaging less than 2 per annum and a guestimated maximum of 3.1 per annum.
(These are people who die from snakebite in remote places and where medical
science does not make a diagnoses).

This translates, roughly, to a mortality rate of 1:8 million per annum.
Distributed roughly among 16 highly venomous snakes. Average per species
thus is 1 fatality per snake species every 8 years. The vaunted "most
venomous snake on earth" the Fierce Snake (Oxyuranus microlepidotus)
has yet to be implicated in a single fatality. The range of the snake is
small and the population extremely thin. So despite the fact that an
average yield of venom from this snake can kill 250 000 rats, just how
dangerous is it?

Russell's Viper

On the other hand the humble Russell's Viper kills humans by the
hundreds. It seldom if ever figures in the "most dangerous snake" lists!
The Cobras of Sri Lanka kill an average 5 people out of every 100 000
population per annum. Translated to the Australian scenario this would
mean around 900 deaths per annum.

What these lists are giving us is the POTENTIALLY most
dangerous snakes. A true list of the most FATAL TO MAN snakes would
give us some very humble but widespread and moderately venomous snakes.

So what's the answer?

There is none - only an answer within defined parameters such as:

The snakes with the largest venom yield

The snakes with the most toxic venom to mice

The snakes that have killed the most humans

So who are the leading contenders?

This list is by no means complete.

Snake

Symptoms

Mortality

Treatment

Asian pit vipers - from 2 to 5 ft. long, throughout Asia

reactions and mortality vary, but most bites cause tissue damage and mortality is generally low.

Australian brown snakes - 4 to 7 ft. long

very slow onset of cardiac or respiratory distress

moderate mortality, but because death can be sudden and unexpected,
it is the most dangerous of the Australian snakes

antivenom.

Barba Amarilla or Fer-de-lance - up to 7 ft. long, from tropical Mexico to Brazil

severe tissue damage common

moderate mortality

antivenom.

Black mamba - up to 14 ft. long, fast-moving, S and C Africa

rapid onset of dizziness, difficulty breathing, erratic heart-beat

mortality high, nears 100%
without antivenom.

antivenom.

Boomslang - under 6 ft. long, in African savannahs

rapid onset of nausea and dizziness, often followed by slight recovery and then sudden death from internal hemorrhaging

mortality low, but amputation of affected digits is sometimes necessary

Mojave rattler may produce temporary paralysis.

antivenom.

Rinkhals, or spitting, cobra - 5 ft. and 7 ft. long, S Africa

squirt venom through holes in front of fangs as a defense

venom is severely irritating and can cause blindness.

antivenom.

Russell's viper or tic-polonga - over 5 ft. long, throughout Asia

internal bleeding

moderate mortality rate, bite reports common

antivenom.

Saw-scaled or carpet viper - up to 2 ft. long, in dry areas from India to Africa

severe bleeding, fever

high mortality, causes more human fatalities than any other snake

antivenom.

Sea snakes - throughout Pacific, Indian oceans except NE Pacific

almost painless bite, variety of muscle pain, paralysis

mortality rate low, many bites are not envenomed

some antivenoms.

Sharp-nosed pit viper or One Hundred Pace Snake - up to 5 ft. long, in S Vietnam and Taiwan, China

the most toxic of Asian pit vipers, very rapid onset of swelling and tissue damage, internal bleeding

moderate mortality

antivenom.

Taipan - up to 11 ft. long, in Australia and New Guinea

rapid paralysis with severe breathing difficulty

mortality nears 100% without antivenom.

antivenom.

Tiger snake - 2 to 6 ft. long, S Australia

pain, numbness, mental disturbances with rapid onset of paralysis

may be the most deadly of all land snakes though antivenom is quite effective.

antivenom.

Yellow or Cape cobra - 7 ft. long, in southern Africa

most toxic venom of any cobra, rapid onset of swelling, breathing and cardiac difficulties

mortality high without treatment

antivenom.

Note: Not all bites by venomous snakes are actually envenomed.
All animal bites, however, possibly carry tetanus, and anyone
suffering a snake bite should seek medical attention.
Antivenoms do not cure they are only an aid in the treatment of bites.
Mortality rates above are for envenomed bites